Increasing the reliability of airbag module assemblies is desirable. In addition, simplifying the assembly process and expanding the design options of airbag module assemblies would be helpful, saving time and reducing costs in an increasingly competitive industry.
An airbag module assembly is part of an inflatable restraint system that automobile manufacturers install in automobiles for protecting an occupant by physically restraining the occupant if the automobile encounters a collision.
Certain types of airbag module assemblies normally include a reaction canister, an inflator, a diffuser, an airbag cushion, and means for securing the assembly together. The reaction canister is formed from extruded aluminum and has an open top through which a portion of the airbag cushion escapes during inflation. The inflator is secured within the canister and contains means for producing the inflation gas for inflating the airbag cushion. The diffuser is also secured within the canister and generally comprises a shelf that encloses the inflator. The diffuser shelf has a plurality of diffusing openings that deliver inflation gas from the inflator to the airbag cushion.
The stored airbag cushion includes a folded portion leading to a generally rectangular open mouth formed by two opposite mouth side edges and two shorter opposite mouth ends. The two mouth side edges are secured to the canister above the diffuser so that inflation gas from the inflator diffuses into the mouth through the diffuser openings in the diffuser shelf.
During inflation of the airbag cushion, inflation gases can escape from between the diffuser and the mouth ends of the airbag cushion. These escaping gases can cause the mouth to collapse inwardly, preventing correct deployment of the airbag cushion. To avoid this, some previous airbag cushions were manufactured with additional strips of cushion material sewn onto the ends of the mouth and secured by the endplates of the canister. However, this method adds greatly to the complexity of the airbag cushion and the airbag module manufacturing process.
Preventing the folded portion of the airbag cushion from becoming pinched by the endplates of the canister during assembly, which can retard the deployment of the airbag upon inflation, has also been a concern. During assembly, the inflator is first secured within the reaction canister. The diffuser and airbag cushion, and the endplates are then attached to close the ends of the canister, containing the airbag cushion therein. Preventing the folded portion of the airbag cushion from becoming pinched by the endplates of the canister has required inspections and the use of controls and sensors on assembly equipment, complicating the manufacturing process.
In addition, since the endplates help contain the folded portion of the airbag cushion within the canister, they must normally be attached to the module assembly after the airbag cushion is installed. Yet, once the endplates are attached the interior of the canister cannot be accessed. The inflator, therefore, must be secured within the canister before the diffuser, airbag cushion and endplates. This factor restricts the order of assembly and also adds to the complexity of manufacturing the airbag module assembly.
Modifying the airbag module assembly or a component of the assembly to prevent the mouth of the airbag cushion from collapsing inwardly during inflation, to prevent the airbag cushion from becoming pinched by the endplates, and to eliminate reliance on the endplates for containing the airbag cushion within the reaction canister would be very helpful. This would increase the reliability, simplify the manufacturing process and reduce the manufacturing costs of the airbag module assembly.